The Earth’s Atmosphere
Notes
1. The Atmosphere
 A thin layer of air that forms a protective covering around the planet
 Gases found in the atmosphere
o Nitrogen – 78%
o Oxygen – 21%
o 1% - trace amounts of other gases
 Solids found in the atmosphere
o dust
o salt
o pollen
 Liquids found in the atmosphere
o water
o up to 4% water vapor
2. Layers of the Atmosphere
 Troposphere
o Closest layer to Earth’s surface - We live here
o All weather occurs here
o 99% of the water vapor is found here
o 75% of all atmospheric gases are found here
o The temperature decreases as you go up in altitude
 Stratosphere
o The ozone layer is found here
 Protects us from the Sun’s ultraviolet rays
o Planes and jets fly here
o The temperature increases as you go up in altitude
 Mesosphere
o Scientists know least about this layer
o Meteors burn up in this layer because of friction with the air molecules
(called “shooting stars”)
o Temperatures decrease as you go up in altitude
o This is the coldest layer
 Thermosphere
o Thickest layer
o Contains the ionosphere
 A layer of electrically charged particles
 Allows radio waves to travel across the country
 Causes the Northern and Southern lights (auroras)
o Temperatures increase as you go up in altitude
 Exosphere
o Very few air molecules which have extremely high energy and
temperatures
o Satellites and space shuttles orbit here
o Temperature increases as you go up in altitude
3. Heat Transfer
 Most of Earth’s energy comes from the Sun
 heat – energy that flows from an object with a higher temperature to an object
with a lower temperature
 Three types of heat transfer
o Radiation – heat transferred through waves or RAYS
 Earth is heated by radiation
 Dirt, rocks, water, concrete, sand, etc. absorb this energy
 Examples
 Feeling the sun on your face
 Sunburn
 Microwaving food
 Feeling the heat from a fire
o Conduction – heat transferred by 2 objects through DIRECT contact
(touching)
 Examples
 Holding a hot cup of hot chocolate
 Touching a hot spoon that has been sitting in a bowl of
hot soup
 Cooking food in a frying pan (the pan sits on the burner
which is heating up and then the food touches the pan)
o Convection – heat transferred through the flow of material (gases and
liquids)
 The heated material rises because it is less dense, it cools, and
sinks because the material becomes more dense
 This is how the atmosphere gets heated
 Examples
 Lava lamps
 Boiling water
 Convection ovens
 Heating a room
4. Winds
 Wind – the movement of air from area of high pressure to an area of low
pressure
o cold air contracts (particles are close together), have high density,
sinks
o warm air expands (particles are spread out), have low density, rises
 Winds are named after the direction they come from
 Global Winds
o Air moves between the equator and the poles
o Coriolis Effect – the rotation of Earth causes the global winds to turn
o Types of Global Winds
 Polar Easterlies
 Located at the south pole and north pole
 Winds come from the East
 Prevailing Westerlies
 Winds come from the West
 This controls our weather in the United States


Trade Winds
 Winds come from the East
 Early sailors used these winds to travel from Europe to
trade goods
 Doldrums
 Located around the equator
 Very little wind
 Consistent low pressure
o Jet Stream
 Narrow bands of winds located at the top of the troposphere
 Winds move west to east
 Form between cold, dry air and warm, moist air
 Jets move faster when flying in the Jet Stream
Local Winds
o Sea Breeze
 The land heats up faster than the ocean causing the warm air
over the land to rise. It cools and sinks over the ocean creating
a cool breeze from the ocean.
 This happens during the day.
o Land Breeze
 The land cools faster than the ocean causing cooler air to sink
over the land. The air warm over the ocean rises. This causes
a warm breeze from the land.
 This happens at night.
5. The Water Cycle (a.k.a. Hydrosphere – all water on the Earth and in the atmosphere)
 Constant cycling of water in the atmosphere
 Plays an important role in determining weather patterns and climate
 The Water Cycle
o Water evaporates (change of matter from a liquid to a gas)
o Plants give off moistures through the surface of their leaves transpiration
o Water condenses (change of matter from a gas to a liquid) and makes
clouds
o The clouds can form precipitation (rain, snow, sleet, or hail)
o Precipitation travels across the Earth’s surface as run off or
groundwater
o The cycle repeats